AQA A-Level Biology: Topics Covered in Paper 1, Exams of Nursing

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AQA A-level Biology paper 1 Question with complete solution2024 large molecules often contain carbon. why? - Correct answers ✅they can readily form bonds with other carbon atoms. this forms a 'backbone'. other atoms can then attach. describe benedicts test for reducing sugars - Correct answers ✅add equal volumes of the sugar sample and benedicts reagent. heat the mixture in a water bath for 5 minutes. brick red precipitate will form. what is a reducing sugar? - Correct answers ✅a sugar that can reduce (give electrons to) another chemical. describe the benedicts test for non reducing sugars - Correct answers ✅with food sample, add an equal volume of dilute hydrochloric acid in a test tube. place test tube in water bath for 5 mins. add sodium hydrogencarbonate solution. heat resulting solution with an equal volume of benedicts. solution for 5 minutes. turns orange/brown. what does dilute hydrochloric acid do in the benedicts test for non reducing sugars? - Correct answers ✅it hydrolyses any disaccharide into monosaccharides, thus also forming reducing sugars. AQA A-level Biology paper 1 Question with complete solution2024 describe the structure of starch - Correct answers ✅chains of alpha glucose some chains are branched= amylopetcin some chains are coiled= amylose what purpose does the structure of amylose serve? - Correct answers ✅makes the molecule compact so it is stored more easily. what purpose does the structure of amylopectin serve? - Correct answers ✅more surface area for enzymes to work on, thus glucose molecules can be released at a much quicker rate. how is the structure of starch suited to its function? - Correct answers ✅1. starch is insolube so it doesnt affect water potential 2. it is large enough that it doesnt diffuse out of cells 3. compact enough so that a lot of it can be stored in a small space 4. branched= each end can simultaneously be acted on by enzymes, so glucose is quickly released how is the structure of glycogen suited to its function? - Correct answers ✅1. insoluble, so no effect on water potential of cell 2. insoluble, so doesnt diffuse out of cells AQA A-level Biology paper 1 Question with complete solution2024 what is meant by 'secondary sequence' of a protein - Correct answers ✅The way in which the primary structure of a polypeptide chain folds e.g. alpha helix or beta pleated sheets. shape is held by H bonds. what is meant by 'tertiary sequence' of a protein - Correct answers ✅This is the overall 3-D structure of the protein. The shape of the protein is held together by H bonds and ionic bonds and disulfide bridges. what is meant by 'quaternary sequence' of a protein - Correct answers ✅If a protein is made up of several polypeptide chains that are linked in various ways, the way they are arranged is called the quaternary structure. describe the test for proteins - Correct answers ✅add equal volumes of sample and sodium hydroxide to a test tube. add a few drops of dilute copper (II) sulfate and mix. if solution turns purple, protein is present. what are fiberous proteins made up of? - Correct answers ✅made of long molecules arranged to form fibres (e.g. in keratin). Several helices may be wound around each other to form very strong fibres. AQA A-level Biology paper 1 Question with complete solution2024 what are globular proteins made up of? - Correct answers ✅made of chains folded into a compact structure. One of the most important classes are the enzymes. Although these folds are less regular than in a helix, they are highly specific and a particular protein will always be folded in the same way. what kind of protein is collagen? - Correct answers ✅fiberous what kind of protein is haemoglobin? - Correct answers ✅globular what is haemoglobin made up of? - Correct answers ✅two α polypeptide chains two β polypeptide chains an inorganic prosthetic haem group (Fe2+) what is collagen made up of? describe its structure? - Correct answers ✅three polypeptide chains wound around each other each of the three chains is a coil itself Hydrogen bonds form between these coils Collagen molecules form further chains with other collagen molecules and form Covalent Cross Links with each other, which are staggered along the molecules to further increase stability. Collagen molecules AQA A-level Biology paper 1 Question with complete solution2024 wrapped around each other form Collagen Fibrils which themselves form Collagen Fibres. what are the functions of collagen? - Correct answers ✅1. Form the structure of bones 2. Makes up cartilage and connective tissue 3. Prevents blood that is being pumped at high pressure from bursting the walls of arteries 4. Is the main component of tendons, which connect skeletal muscles to bones what type of bond forms between the phosphate group and deoxyribose sugar in DNA? - Correct answers ✅phosphodiester bond why is DNA stable? - Correct answers ✅1. the phosphodiester backbone protects the more chemically reactive organic bases inside the double helix 2. many hydrogen bonds link the base pairs together, so it adds strength overall. how is DNA adapted to carrying out its function? - Correct answers ✅1. it is very stable, thus rarely mutates 2. the H bonds can easily be separated during DNA replication and protein synthesis AQA A-level Biology paper 1 Question with complete solution2024 transport, modify and store lipids form lysosomes what is meant by 'organ'? - Correct answers ✅a combination of tissues that are coordinated to perform a variety of functions. describe binary fission - Correct answers ✅the circular DNA molecule replicates and both copies attach to the cell membrane. plasmids also replicate cell membrane grows between the two DNA molecules, dividing the cytoplasm into two. a new cell wall forms between the two DNA molecules. two daughter cells are produced, each with a single copy of circular DNA and a variable number of plasmids. how do viruses replicate? - Correct answers ✅they attach to their host cell with their attachment proteins. nucleic acids are injected into host cell. the genetic info contains "instructions" for the host cells metabolic processes to start producing the viral components, which are assembled into new viruses. describe cell mediated immunity - Correct answers ✅1. phagocytes injest pathogens. AQA A-level Biology paper 1 Question with complete solution2024 2. the phagocyte places antigens from pathogen on its cell surface membrane, so it becomes an antigen presenting cell. 3. receptors of T-helper cells have a complimentary fit to these antigens. 4. this attachment activates T cells to divide rapidly by mitosis and form a clone of genetically identical cells. 5. the cloned T cells: a. develop into memory cells b. stimulate phagocytosis c. stimulate B cells to divide and secret their antibody d. activate cytotoxic T cells. describe humoral immunity - Correct answers ✅1. the surface antigen of a pathogen is taken up by B cell 2. the B cell processes it and presents the antigen on its surface 3. T-helper cells attach to the processed antigens, thus activating the B cell 4. B cells divide by mitosis to produce a clone of plasma cells 5. these secrete the specific antibody that can bind to the pathogens antigen 6. the antigens destroy the pathogen 7. some B cells develop into memory cells AQA A-level Biology paper 1 Question with complete solution2024 what is passive immunity and how is it produced? - Correct answers ✅produced by the introduction of antibodies into individuals from an outside source. immunity is acquired immediately. no contact with pathogen/s needed. short term immunity: antibodies aren't replaced when broken down, memory cells not formed. e.g. anti-venom what is active immunity and how is it produced? - Correct answers ✅produced by stimulating the production of antibodies by the individuals own immune system. contact with pathogen/s needed. immunity takes time to develop natural active immunity - Correct answers ✅results from an individual becoming infected with a disease under normal circumstances. long term body produces its own antibodies artificial active immunity - Correct answers ✅involves inducing an immune response in an individual WITHOUT them suffering the symptoms of the disease. AQA A-level Biology paper 1 Question with complete solution2024 2. a diffusion gradient is established 3. The ends of tracheoles are in contact with individual cells, contain a small amount of fluid in which the gases are dissolved. The fluid is drawn into the muscle tissue during exercise. This increases the surface area of air in contact with the cells. Gases diffuse in through the spiracles and down the tracheae and tracheoles. describe and explain the countercurrent exchange principle - Correct answers ✅-the blood and the water flow in opposite directions -blood that is loaded with O2 meets water, which already has maximum O2 -blood with little O2 meets with water with O2 removed -so, diffusion concentration gradient established and maintained across the entire width of the gill lamellae -so, 80% of O2 in water absorbed into fish blood how does the structure of a plant leaf link to gas exchange? - Correct answers ✅-all cells are close to stomata, and therefore surface, therefore a short diffusion pathway -inter-connecting air spaces in the mesophyll so that gases can readily contact mesophyll cells describe and explain why plant stomata links to gas exchange and its benefits - Correct answers ✅stomata are like minute pores, on the underside of leaves. AQA A-level Biology paper 1 Question with complete solution2024 each has guard cells, which control the rate of gas exchange guard cells close when water loss is excessive how do insects limit water loss? - Correct answers ✅-small surface area to volume ratio -waterproof coverings -spiracles which can close how do xerophytes limit water loss? - Correct answers ✅-thick waxy cuticle -rolled up leaves: traps water vapour -hairy leaves: traps moist air -stomata in pits/grooves: traps moist air -reduced surface area to volume ratio by trapping air, water potential gradient is reduced describe the process of inspiration - Correct answers ✅external intercostals contract internal intercostals relax ribs move up and outwards, increasing thorax volume diaphragm contracts, further increasing thorax volume AQA A-level Biology paper 1 Question with complete solution2024 air pressure in lungs becomes lower than atmospheric pressure, so air is forced in describe the process of expiration - Correct answers ✅internal intercostals contract external intercostals relax ribs movie in and downwards diaphragm relaxes this decreases thorax volume air pressure in lungs becomes greater than atmospheric pressure, so air is forced out structure of haemoglobin - Correct answers ✅4 polypeptide chains - 2 alpha - 2 beta each chain has a haem group which contains a ferrous Fe2+ ion. what is the vena cava connected to? - Correct answers ✅right atrium what is aorta connected to? - Correct answers ✅left ventricle what is pulmonary artery connected to? - Correct answers ✅right ventricle AQA A-level Biology paper 1 Question with complete solution2024 how does water travel into/through plants? - Correct answers ✅the water particles have higher water potential than the root hair cell, and so they enter the cell by osmosis down a water potential gradient. the water potential of the root hair cell is now higher than the cortex cell, and so water enters the cortex cell by osmosis. symplast pathway: water enters root hair cell by osmosis, and travels from the cytoplasm of one cell to another by plasmodesmata apoplast pathway: water enters the root by entering the spaces in cell walls. water moves up xylem due to H bonding in water. water travels until it reaches the casparian strip, where water needs to travel via symplast pathway. what is plasmodesmata? - Correct answers ✅strands of cytoplasm linking one cell to another that passes through pores in cellulose cell walls explain cohesion-tension theory - Correct answers ✅water is drawn from cell to cell by osmosis. it moves across the root cortex to keep a constant column of water. this creates 'tension' on the column of water in the xylem. AQA A-level Biology paper 1 Question with complete solution2024 water shows cohesion due to its H bonding. this makes the column very strong. so, water is pulled up the xylem to replace the water lost by evaporation. water moves between the cells of a leaf along the water potential gradient. what is the role of companion cells? - Correct answers ✅they load/unload organic solutes into the sieve tube describe the transfer of sucrose into sieve elements - Correct answers ✅sucrose is manufactured from photosynthesising cells. it diffuses by facilitated diffusion from photosynthesising cells to companion cells, down a concentration gradient. H+ actively transported into the spaces between cell walls. H+ diffuses into sieve tube elements. sucrose molecules also transported with them, through co-transport. what is a 'source' cell? - Correct answers ✅cells that photosynthesise and make sugars what is a 'sink' cell? - Correct answers ✅cells that use/store organic solutes AQA A-level Biology paper 1 Question with complete solution2024 explain mass flow hypothesis - Correct answers ✅1. sugars build up at source, lowering water potential of source cells. 2. water therefore enters cells by osmosis. 3. sugars are then actively transported into sieve tubes by transfer cells 4. this lowers water potential in sieve tube, so water enters by osmosis. 5. this causes high pressure potential at source at sink, sugars are unloaded by companion cells 6. this raises water potential how can you investigate mass flow using aphids? - Correct answers ✅1. cut across their mouthparts. the mouthparts act as a sampling tube that they collect the phloem contents. 2. If the phloem is punctured with a hollow tube then the sap oozes out, showing that there is high pressure (compression) inside the phloem (this is how maple syrup is tapped). 3. If the xylem is punctured then air is sucked in, showing that there is low pressure (tension) inside the xylem. how can you investigate transport using radioactive tracers? - Correct answers ✅a plant is supplied with 14C, which becomes incorporated into organic substances in the plant. AQA A-level Biology paper 1 Question with complete solution2024 so, new genetic combinations of maternal and paternal alleles are produced what is ATP made up of? - Correct answers ✅adenine ribose 3 phosphates how does ATP store energy? - Correct answers ✅has 3 phosphates, the bonds between these are unstable and so have a low activation energy, hence easily broke. when they break, they release energy. what does ATP synthase catalyse? - Correct answers ✅the formation of ATP from ADP in what scenarios is ATP reformed? - Correct answers ✅during photosynthesis, in chlorophyll containing plants during respiration (oxidative phosphorylation) substrate level phosphorylation why is ATP a good immediate energy source in a cell - Correct answers ✅the instability of the phosphate bonds. each ATP molecule releases less energy than glucose molecule, and so is smaller and more manageable AQA A-level Biology paper 1 Question with complete solution2024 the hydrolysis of ATP to ADP is a single reaction that releases immediate energy what energy requiring processes need ATP? - Correct answers ✅metabolic processes movement active transport secretion activation of molecules which has a longer wavelength: light or a beam of electrons? - Correct answers ✅light what are the two types of electron microscope? - Correct answers ✅transmission electron microscope scanning electron microscope how does a transmission electron microscope work? - Correct answers ✅it has an electron gun which produces a beam of electrons this is focused onto a specimen by condenser electromagnets the beam passes through the specimen some parts of the specimen absorb the electrons and appear dark and vice versa AQA A-level Biology paper 1 Question with complete solution2024 an image is produced why cant the highest resolution images not be produced by TEM? - Correct answers ✅there are difficulties preparing the specimen, which can limit resolution a higher energy electron beam may destroy the specimen how does a scanning electron microscope work? - Correct answers ✅it directs an electron beam onto a specimen surface rather than penetrating it. the beam is passed back and forth across a specimen in a regular pattern, depending on its contours a computer is used to build up a 3D image how to calibrate an eyepiece graticule? - Correct answers ✅use a stage micrometer and align it with the eyepiece graticule. then, calculate the length of each subdivision define ecology - Correct answers ✅the study of the inter-relationships between organisms and their environment, including abiotic and biotic factors. define ecosystem - Correct answers ✅dynamic systems made up of a community and all the non-living factors of its environment. It includes AQA A-level Biology paper 1 Question with complete solution2024 be produced at a faster rate in a secondary immune response, and so the pathogen can be destroyed faster. Describe how carbon dioxide in the air outside a leaf reaches mesophyll cells inside the leaf (3) - Correct answers ✅it enters via stomata, which are opened as guard cells open. if diffuses down a concentration gradient through the air spaces. There are large numbers of mitochondria in the epithelial cell. Explain how these organelles help the cell to absorb the products of digestion. (2) - Correct answers ✅mitochondria provide the ATP this is needed for active transport of substances into the cell red blood cells are biconcave discs. Explain one advantage of a biconcave disc over a spherical cell of the same volume in transporting oxygen. - Correct answers ✅Large (surface) area; For diffusion; Describe how oxygen in air in the alveoli enters the blood in capillaries. - Correct answers ✅diffusion across alveoli epithelium Attaching lactase to the beads is a more efficient use of lactase than adding the lactase directly to cow's milk. AQA A-level Biology paper 1 Question with complete solution2024 Suggest three reasons why it is more efficient to attach lactase to the beads. - Correct answers ✅lactase bead can be reused continuous process lactase not present in milk what is a vaccine? - Correct answers ✅Contains antigen / proteins / dead / weakened microorganism / pathogen / virus / bacteria; Stimulates production of antibodies / plasma cells / memory cells where is amylase produced? - Correct answers ✅salivary glands, pancreas, small intestine where is maltase produced? - Correct answers ✅epithelium of small intestine where is lactose produced? - Correct answers ✅pancreas, small intestine where are proteases produced? - Correct answers ✅stomach, pancreas, small intestine describe the involvement of RER in producing chylomicrons - Correct answers ✅RER synthesises proteins in the ribosomes, which are needed to form chylomicrons. AQA A-level Biology paper 1 Question with complete solution2024 suggest how chylomicrons leave the epithelial cell. - Correct answers ✅by exocytosis because theyre too large to leave by other methods whats the difference between species richness and diversity index? - Correct answers ✅Species richness measures only number of (different) species / does not measure number of individuals. directional selection - Correct answers ✅selection favours individuals in one direction from the mean of the population. e.g. when environment changes, those with advantageous allele outside of the mean will be more likely to survive and breed. stabilising selection - Correct answers ✅if environmental conditions are the same, those with alleles closer to the mean are favored. they are more likely to survive and reproduce e.g. birth weight. courtship behaviour results in reproductive success by... - Correct answers ✅1. allowing recognition of own species 2. identifying those capable of breeding 3. forming a pair bond 4. synchronising mating